Human chronotypes from a theoretical perspective

PLoS One. 2013;8(3):e59464. doi: 10.1371/journal.pone.0059464. Epub 2013 Mar 27.


The endogenous circadian timing system has evolved to synchronize an organism to periodically recurring environmental conditions. Those external time cues are called Zeitgebers. When entrained by a Zeitgeber, the intrinsic oscillator adopts a fixed phase relation ψ to the Zeitgeber. Here, we systematically study how the phase of entrainment depends on clock and Zeitgeber properties. We combine numerical simulations of amplitude-phase models with predictions from analytically tractable models. In this way we derive relations between the phase of entrainment ψ to the mismatch between the endogenous and Zeitgeber period, the Zeitgeber strength, and the range of entrainment. A core result is the "180° rule" asserting that the phase ψ varies over a range of about 180° within the entrainment range. The 180° rule implies that clocks with a narrow entrainment range ("strong oscillators") exhibit quite flexible entrainment phases. We argue that this high sensitivity of the entrainment phase contributes to the wide range of human chronotypes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Circadian Clocks / physiology*
  • Environment
  • Humans
  • Models, Biological*
  • Time Factors

Grants and funding

The authors thank the BMBF (BCCN, grant 01GQ1001C) and the DFG (SFB 618, SPP 1395, GRK 1742) for financial support. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.